Rework analysis server performance measurement code.

pkg/analyzer/lib/src/generated/source_io.dart

Index: pkg/analyzer/lib/src/generated/source_io.dart
diff --git a/pkg/analyzer/lib/src/generated/source_io.dart b/pkg/analyzer/lib/src/generated/source_io.dart
index e0078d5987992681545ecc8d455f9352ff002b18..afc50ff5491a76c002cdb437a4ecc5130e40ac14 100644
--- a/pkg/analyzer/lib/src/generated/source_io.dart
+++ b/pkg/analyzer/lib/src/generated/source_io.dart
@@ -129,11 +129,11 @@ class FileBasedSource extends Source {
 
   @override
   TimestampedData<String> get contents {
-    TimeCounter_TimeCounterHandle handle = PerformanceStatistics.io.start();
+    PerformanceTag prevTag = PerformanceStatistics.io.makeCurrent();
     try {
       return contentsFromFile;
     } finally {
-      _reportIfSlowIO(handle.stop());
+      prevTag.makeCurrent();
     }
   }
 
@@ -235,23 +235,6 @@ class FileBasedSource extends Source {
     }
     return file.getAbsolutePath();
   }
-
-  /**
-   * Record the time the IO took if it was slow
-   */
-  void _reportIfSlowIO(int nanos) {
-    // TODO(brianwilkerson) Decide whether we still want to capture this data.
-//    //If slower than 10ms
-//    if (nanos > 10 * TimeCounter.NANOS_PER_MILLI) {
-//      InstrumentationBuilder builder = Instrumentation.builder2("SlowIO");
-//      try {
-//        builder.data3("fileName", fullName);
-//        builder.metric2("IO-Time-Nanos", nanos);
-//      } finally {
-//        builder.log();
-//      }
-//    }
-  }
 }
 
 /**